Add --data-dir CLI argument to replace symlink-based data persistence

The Docker entrypoint previously created symlinks from /app/ to /app/data/
so that scripts writing relative paths would persist to the mounted volume.
This caused symlink loops in production when stale symlinks leaked into the
host data directory.

Instead, all scrapers, merge_and_map.py, regen_map.py, and run_all.sh now
accept a --data-dir argument (default: ".") that controls where data files
are read from and written to. The entrypoint and crontab pass
--data-dir /app/data, eliminating the need for symlinks entirely.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

merge_and_map.py

@@ -7,6 +7,7 @@ PSN a CityHome mají při deduplikaci prioritu (načtou se první).
 """
 from __future__ import annotations
 
+import argparse
 import json
 import re
 from pathlib import Path
@@ -40,7 +41,7 @@ def dedup_key(estate: dict) -> str:
     return f"{street}_{price}_{area}"
 
 
-def main():
+def main(data_dir: str = "."):
     # Definice zdrojů — PSN a CityHome jako první (mají prioritu při deduplikaci)
     sources = [
         ("PSN",         "byty_psn.json"),
@@ -51,10 +52,11 @@ def main():
         ("iDNES",       "byty_idnes.json"),
     ]
 
+    data_path = Path(data_dir)
     all_estates = []
 
     for label, filename in sources:
-        path = Path(filename)
+        path = data_path / filename
         if path.exists():
             data = json.loads(path.read_text(encoding="utf-8"))
             # Ensure source is set (Sreality legacy)
@@ -111,7 +113,7 @@ def main():
         print(f"  {src}: {count}")
 
     # Save merged data
-    merged_path = Path("byty_merged.json")
+    merged_path = data_path / "byty_merged.json"
     merged_path.write_text(
         json.dumps(deduplicated, ensure_ascii=False, indent=2),
         encoding="utf-8",
@@ -119,8 +121,12 @@ def main():
     print(f"\n✓ Sloučená data: {merged_path.resolve()}")
 
     # Generate map
-    generate_map(deduplicated)
+    generate_map(deduplicated, output_path=str(data_path / "mapa_bytu.html"))
 
 
 if __name__ == "__main__":
-    main()
+    parser = argparse.ArgumentParser(description="Merge scraped data and generate map")
+    parser.add_argument("--data-dir", type=str, default=".",
+                        help="Directory for reading/writing data files (default: current dir)")
+    args = parser.parse_args()
+    main(data_dir=args.data_dir)